1. Field of the Invention
This invention relates to a tool pot separation type chain which is used to receive, in a tool pot thereof, an exchangeable tool to be used by a machining center and feed the exchangeable tool.
2. Description of the Related Art
A tool pot separation type chain provided for a tool magazine of a machine tool such as a machining center is conventionally known and disclosed, for example, in Japanese Utility Model Laid-Open Publications Nos. Hei-2-27834 and Hei-5-93736. Particularly, the tool pot separation type chain disclosed in Japanese Utility Model Laid-Open Publication No. Hei-5-93736 is shown in FIGS. 7 and 8. Referring to FIGS. 7 and 8, the tool pot separation type chain includes a pair of link plates on which a pair of bearings of a small size are mounted, respectively, such that outer races of the bearings are moved in rolling contact on a guide rail provided for a tool magazine to carry an exchangeable tool with a reduced traveling resistance to the chain. In particular, the tool pot separation type chain 31 includes a plurality of pairs of inner and outer link plates 33 and 34 each having a tool pot receiving section in which a tool pot 32 for holding an exchangeable tool is removably accommodated. The link plates 33 and 34 in each two adjacent pairs are connected to each other by a connection pin 36 with a roller 35 disposed between the pair of inner link plates 33, 33. A receiving section center line axe2x80x94a interconnecting the centers of the tool pot receiving sections of the link plates 33 and 34 coincides with a chain pitch line which is also denoted by axe2x80x94a. A pin 37 extends between the link plates 33 and 34 in each pair in parallel to the connection pin 36 of the link plates 33 and 34 just below the tool pot receiving sections such that it projects outwardly from the link plates 33 and 34. A pair of small bearings 38 are fitted on the pin 37 on the exterior side of the outer link plates 34, 34. Further, a guide rail 40 along which outer races 38A of the bearings 38 roll is mounted on a tool magazine frame 39, and also a pair of tool pot jumping-out preventing rails 41A and 41B are provided on the tool magazine frame 39 in an opposing relationship to the guide rail 40 so that the tool pot 32 may not come out of the tool pot receiving sections while they are fed.
In a tool carrying apparatus provided for a tool magazine, the traveling direction of a tool pot separation type chain is usually changed or reversed by a guide roller, a sprocket wheel, a guiding curved rail or the like in a circulating path thereof such that it travels in a vertical upward or downward direction, a horizontal direction, an oblique upward or downward direction or the like. Therefore, in the conventional tool pot separation type chain 31 described above, although a tool pot moves in rolling contact with the guide rail 40 through the outer races 38A at a place where the tool pot separation type chain 31 travels horizontally on the guide rail 40, at another place along which the tool pot travels horizontally on the tool pot jumping-out preventing rails 41A and 41B after it is reversed, the tool pot travels in sliding contact with the tool pot jumping-out preventing rails 41A and 41B. Consequently, in the tool pot separation type chain 31, some tool pots always remain in sliding contact with the rails at some place along the path of circulation. As a result, the tool pot separation type chain 31 is acted upon by a high resistance to its traveling movement. Therefore, the conventional tool carrying apparatus is disadvantageous in terms of requirement for a high driving source, abrasion of a tool pot and a jumping-out preventing rail, and noise generated by a slip in sliding contact.
Further, in the tool pot separation type chain 31, when it is tried to carry in and load or carry out and unload a tool pot 32 into or from the tool pot receiving sections of the link plates 33 and 34 by means of a gripper apparatus or the like at a tool pot loading/unloading position intermediate along a vertical portion of the path of circulation of the tool pot separation type chain 31 (refer to FIG. 6), the tool pot 32 is slidably moved on a carrying in/out rail 18 which extends horizontally. Therefore, the conventional tool pot separation type chain 31 is disadvantageous in that the tool pot 32 is acted upon by high resistance to movement by the sliding contact and cannot be loaded or unloaded readily and besides a tool pot and the carrying in/out rail 18 suffer from abrasion.
The conventional tool pot separation type chain 31 is further disadvantageous in that, since the bearings 38 are mounted on the link plates 33 and 34 themselves, a great number of parts are required to mount the bearings 38, and the size of the bearings 38 is limited from two factors of the magnitudes of the link plate and the tool pot and a bearing of a large size cannot be used for the bearings 38. Furthermore, in the conventional tool pot separation type chain 31, while it moves horizontally, the force for moving the weight of tools and the tool pot 32 is assigned to the chain, and the bearings 38 mounted on the chain support the overall weight. Further, also the tensile force upon movement is assigned to the chain. Consequently, the chain is acted upon by the two forces. Accordingly, the conventional tool pot separation type chain 31 is liable to suffer from abrasion or elongation of the chain and is disadvantageous in durability. Further, in the conventional tool pot separation type chain 31, depending upon whether the chain which travels downwardly in the tool magazine thereafter changes its traveling direction upwardly around a lower corner portion or the chain which travels upwardly thereafter changes its traveling direction downwardly around an upper corner portion, the radii of curvature of rails which may be provided at such corners must be made different from each other. Further, a sprocket wheel meshes with the chain on the bearing side while another sprocket wheel meshes with the chain on the reverse side. Therefore, in order to prevent a pin for mounting a bearing from interfering with a link plate, sprocket wheels of different shapes are required.
It is an object of the present invention to provide a tool pot separation type chain which minimizes a traveling resistance thereof during carrying of a tool pot to reduce the driving force, prevent abrasion of a tool pot and a rail and suppress generation of noise, and which facilitates a carrying in or carrying out operation of a tool pot at a tool pot loading/unloading position.
In order to attain the object described above, according to the present invention, there is provided a tool pot separation type chain for use in a tool magazine having a guide rail and a tool pot jumping-out preventing rail provided in an opposing relationship with each other along a circulating traveling path of the chain. The chain comprises a tool pot, and a plurality of pairs of laterally aligned link plates each adjacent ones of which are connected to each other by a connection pin, each of the pairs of link plates having a tool pot receiving section for removably receiving therein the tool pot. The tool pot has at least one bearing mounted thereon, and the bearing has an outer race movable in rolling contact on the guide rail or the tool pot jumping-out preventing rail of the tool magazine.
In one preferred form of the present invention, the link plates each have a pair of grip fingers pivotally mounted thereon and disposed on opposite sides of the tool pot receiving section, and a spring member acting between the grip fingers and urging them toward each other so that the tool pot received in the tool pot receiving section is held by and between the grip fingers under a biasing force of the spring member.
It is preferable that the tool pot has an outer peripheral surface formed with two pairs of recesses, and the grip fingers has a pair of hooks provided at respective free ends thereof and lockingly engageable with each pair of recesses.
In the tool pot separation type chain, the outer race of the bearing provided on the tool pot moves in rolling contact on the guide rail or tool pot jumping-out preventing rail provided in the tool magazine. Consequently, a great number of tools to be exchanged and the tool pot can be carried by a comparatively low driving force without generation of noise.
More specifically, since the bearing whose outer race moves in rolling contact with the guide rail or tool pot jumping-out preventing rail provided in the tool magazine is mounted on the tool pot which is removably received in each of the tool pot receiving sections of the link plates, at a place where the tool pot separation type chain travels in a horizontal direction in a circulating path thereof, the outer race of the bearing moves in rolling contact on the guide rail or tool pot jumping-out preventing rail. Consequently, the moving resistance to the tool pot separation type chain in the horizontal direction can be reduced. Consequently, since the tool pot separation type chain involves no sliding contact with any member including the guide rail and the tool pot jumping-out preventing rail along the circulating path thereof, the tool pot separation type chain can be driven with a comparatively low driving force. As a result, abrasion of the tool pot and rails and generation of noise can be prevented.
When a tool pot is loaded or unloaded in a horizontal direction at a tool pot loading/unloading position along a vertical traveling path of a tool pot separation type chain, in the conventional tool pot separation type chain described hereinabove, since no bearing is provided on the tool pot itself, the tool pot moves in sliding contact on a carrying in/out rail so as to be carried out or in, and consequently, the resistance to the movement is high and the carrying in/out operation of the tool pot is difficult and besides noise is generated. However, in the tool pot separation type chain of the present invention, since the bearing is provided on the tool pot, the outer race of the bearing moves in rolling contact on a tool pot carrying in/out rail provided horizontally. Consequently, the resistance to the movement is low, and reduction of the driving force for the movement can be achieved. Further, abrasion of the tool pot and the carrying in/out rail and generation of noise upon loading/unloading of a tool pot can be reduced, and the carrying in/out operation of a tool pot can be performed readily.
Further, since the bearing is mounted on the tool pot itself, the number of parts can be reduced when compared with the alternative arrangement wherein a bearing is mounted on each link plate. Consequently, the tool pot separation type chain can be produced readily and simply. Furthermore, when the tool pot separation type chain moves in a horizontal direction along the circulating path thereof, the weight of a tool and a tool pot and the weight of the chain are supported by the bearings provided on the tool pot, and the tensile force upon movement is supported by the chain. Since the individual forces are assigned separately to the tool pot side and the chain side in this manner, the tensile force to act upon the chain can be minimized. Consequently, elongation of the chain by abrasion can be reduced and the durability of the chain can be achieved.
In addition, different from the conventional separation type chain wherein bearings are mounted on a pin which extends through a pair of link plates, the tool pot separation type chain of the present invention does not include a pin for mounting a bearing and the bearing is provided on the tool pot itself. Consequently, both where the chain which travels downwardly in the tool magazine turns around a lower corner portion and changes its advancing direction to the upward direction and where the chain which travels upwardly turns around an upper corner portion and changes its advancing direction to the downward direction, the radii of curvature of the rails provided at the corner portions need not be made different from each other. Also sprocket wheels provided at the corner portions need not be made different from each other in configuration.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols.